1. Field of Invention
The present invention relates to a reflectance-type liquid crystal display apparatus, and more particularly, to a reflectance-type liquid crystal display apparatus having a light scattering device arranged to enlarge the viewing angle range of the user while preventing light interference, decreased light intensity and reflectance and differences in cell gap distance.
2. Description of the Related Art
A liquid crystal display (LCD) apparatus has been widely used as a display for a portable television and a notebook computer. Liquid crystal display apparatuses are classified into two types. One type is a transmitting-type liquid crystal display apparatus using a backlight as a light source. The other type is a reflectance-type liquid crystal display apparatus which uses sunlight or an indoor lamp as an external light source.
It is hard to decrease the weight, the volume, the cost, and the power consumption of the transmitting-type LCD because the backlight is required. Accordingly, a lot of research and development has been conducted relating to reflectance-type LCDs.
Conventionally, the reflectance-type LCD uses a reflector having an uneven reflecting surface on a lower substrate or a light scattering film on an upper substrate, to enlarge the viewing angle of the user.
The light scattering film scatters the incident light in arbitrary directions to increase a viewing range of the user. However, when using the light scattering film, it is difficult to control the reflectance characteristics such as the reflectance luminance in a certain direction.
On the other hand, when using the reflector having the uneven reflecting surface, it is easy to control the reflectance characteristics by using an uneven reflecting surface having convex and concave portions which are regularly arranged, but light interference is caused by the regular reflection of light as shown in FIG. 1 which illustrates the reflectance I with respect to the viewing angle xcex8 of the user.
Further, if an uneven reflecting surface having convex and concave portions which are randomly arranged is used to prevent the light interference, a uniform reflectance cannot be obtained in the main viewing angle range of the user. As seen in FIG. 2, a high reflectance in a region A is caused by light reflected by parallel portions of the uneven reflecting surface with respect to the substrates, and a low reflectance in a region B is caused by light reflected by oblique portions of the uneven reflecting surface with respect to the substrates. Furthermore, when using an uneven reflecting surface having convex and concave portions which are randomly arranged, it is also difficult to control the reflectance characteristics as when using the scattering film, the cell gap is not uniform because of the uneven reflecting surface, and uniform alignment cannot be achieved by rubbing because the rubbed alignment layer has an uneven surface like the uneven reflecting surface.
To overcome the problems described above, preferred embodiments of the present invention provide a reflectance-type liquid crystal display apparatus which achieves a very wide viewing angle range of the user and is arranged to easily and accurately control the reflectance characteristic while preventing light interference, decreased light intensity and reflectance and differences in cell gap distance.
A reflectance-type liquid crystal display apparatus according to a preferred embodiment of the present invention includes first and second substrates, a light scattering unit on the first substrate, an uneven layer on the second substrate, the uneven layer having an uneven surface, a reflecting layer disposed along the uneven surface, and a liquid crystal layer between the first and second substrates.
According to preferred embodiments of the present invention, the apparatus can be constructed such that the light scattering unit has a plurality of light scattering sources arranged substantially randomly, and the uneven surface preferably has a plurality of convex and concave portions arranged substantially regularly. The reflecting layer having the uneven surface reflects and scatters light in regular directions, and thereby, a desired reflectance characteristic can be easily obtained by controlling the regular arrangement of the uneven surface. The light scattering unit scatters light in random directions to prevent light interference caused by the light reflection in regular directions.
According to another preferred embodiment of the present invention, the light scattering unit preferably includes a plurality of light scattering sources arranged substantially regularly, and the uneven surface has a plurality of convex and concave portions arranged substantially randomly. The light scattering unit scatters light in regular directions, and thereby a desired reflectance characteristic can be easily obtained by controlling the regular arrangement of the light scattering sources. The reflecting layer having the uneven surface scatters light in random directions to prevent light interference caused by the light scattering in regular direction.
Other features, advantages and elements of the present invention will be described in more detail below with reference to the attached drawings.